This invention relates to a vacuum insulating glass (IG) unit, and a method of making the same. More particularly, this invention relates to a method of plasma enhanced evacuation of the internal cavity of a vacuum IG unit or thermally insulating panel.
Vacuum IG units are known in the art. For example, see U.S. Pat. Nos. 5,664,395; 5,657,607; 5,897,927; 5,902,652; and 6,261,652, the disclosures of which are all hereby incorporated herein by reference.
Prior art FIGS. 1-2 illustrate a conventional vacuum IG unit. IG unit 1 includes a pair of spaced apart glass substrates 2 and 3 which enclose an evacuated or low pressure space/cavity 6 therebetween. Glass sheets/substrates 2 and 3 are interconnected by peripheral or edge seal 4 of fused solder glass. An array of support pillars or spacers 5 are provided between the substrates in order to space substrates 2, 3 from one another in order to form the space/cavity 6.
In order to evacuate the space/cavity 6, pump out tube 8 is hermetically sealed by solder glass 9 to an aperture or hole 10 which passes from an interior surface of substrate 2 to the bottom of recess 11 formed in the exterior face of substrate 2. A vacuum pump (not shown in FIGS. 1-2) is attached to pump out tube 8, so that the interior cavity 6 between substrates 2 and 3 can be evacuated (i.e., pumped out) to create low pressure in cavity/space 6. Following evacuation, tube 8 may be melted to seal the vacuum. Optionally, a chemical getter 12 may be included within recess 13.
Interior cavity 6 of vacuum IG units are typically evacuated down to a pressure below 10xe2x88x923 Torr, and most preferably to a pressure below about 10xe2x88x924 Torr of atmospheric pressure. Unfortunately, it typically takes twelve minutes or more in order to evacuate cavity 6 to such a low pressure. This lengthy period of time is sometimes undesirable, as it increases the time of production and ties up the operation of valuable capital-intensive machinery.
In view of the above, it will be appreciated by those skilled in the art that there exists a need for a method of evacuating a vacuum IG unit, which takes less time. It is a purpose of certain embodiments of this invention to fulfill this need, and/or other needs which will become apparent to those skilled in the art as a result of the instant disclosure.
An object of this invention is to provide a method of evacuating a thermally insulating panel such as a vacuum insulating glass (IG) unit, where it takes no more than twelve minutes to evacuate the internal cavity down to a pressure of about 5xc3x9710xe2x88x924 or less.
Another object of this invention is to ignite a plasma within the internal cavity of a thermally insulating panel (e.g., vacuum IG unit) during the evacuation process, in order to speed up and/or improve the process of evacuation.
Another object of this invention is to inject a gas (e.g., argon, nitrogen, oxygen, hydrogen, etc.) into the internal cavity of a thermally insulating panel, and thereafter inductively ignite a plasma within the cavity by at least partially ionizing the gas. It has been found that the ignition of this plasma results in a quicker and/or more efficient evacuation of the cavity. Moreover, it has been found that the ignition of such a plasma during the evacuation process results in a final vacuum IG unit which tends to be more stable upon exposure to ultraviolet (UV) light.
Another object of this invention is to ignite a plasma within the cavity of a thermally insulating panel during an evacuation process, by utilizing an electromagnetic wave generating coil located outside of the cavity.
Another object of this invention is to fulfill one or more of the above-listed objects and/or needs.
Certain example embodiments of this invention fulfill one or more of the above-listed objects and/or needs by providing a method of making a thermally insulating panel, the method comprising:
providing a plurality of spacers between first and second substrates in order to space the substrates from one another;
forming a seal located at least partially between the substrates so as to seal off a space between the substrates; and
causing a plasma to be present in at least a portion of the space between the substrates during a process of evacuating the space.